High intensity railroad crossing signals with separate frequencies of repetition for lamps and relay flasher



June 25, 1968 HIGH 'INTENSIT FREQUENCIES F REPETITION FOR LAMPS AND RELAY FLASHER Filed Sept. 12, 1966 2 Sheets-Sheet l TRIGGER TRIGGER TRANSFORMER TRANSFORMER 33 HI FQ q. 2. 6H 329 VOL TAGE /45 SUPPLY az izs 4/ 11/ PS A INVENTORS, FLASHER Z$"i7)f2 30-48 CPS BY 4/ 44 1/ 44 fiK ML -12 V arr'ommv.

CROSSING SIGNALS WITH SEPARATE FREQUENCIES 01-" REPETITION FOR LAMPS AND RELAY FLASHER June 25, 1968 H. A. SCOTT ETAL.

HIGH INTENSITY RAILROAD 2 Sheets-Sheet :3

Filed Sept.

wmx

United States Patent 3,390,304 HIGH INTENSITY RAILROAD CROSSING SIGNALS WITH SEPARATE FREQUENCIES OF REPETI- TION FOR LAMPS AND RELAY FLASHER Harrison A. Scott, Minneapolis, Minn., and James E. Moe, Ridgewood, N.J., assignors to Railroad Accessories Corporation, Cresskill, NJ.

Filed Sept. 12, 1966, Ser. No. 578,591 9 Claims. (Cl. 315-217) ABSTRACT OF THE DISCLOSURE A high intensity railroad crossing signal comprising a pair of gas discharge lamps mounted within the existing lamp housings of such a signal and power supply therefor connected to the existing flasher relay of the installation. The high voltage power supply is of the type commonly used in automobiles to replace older multivi-brator types and it is connected to the flasher relay terminals such as to be continuously energized by the direct current supplied thereto.

Rather than merely alternately energizing the high intensity flash lamps at the usual 30 to 48 cycles per minute rate of existing railroad crossing signals, during each of its energization intervals a lamp is multiply-energized approximately five times at a rate of approximately ten cycles per second. The flash lamps are thus repeatedly energized for a period of 10 to milliseconds each time, this being the average integration time of the human eye. The ten cycles per second flash rate produces the psychological impression that the lamps are each on half of the time.

Each of a pair of unijunction transistor, resistor-capacitor, pulser circuits is connected to the flasher relay terminals corresponding to each lamp. This controls a solid state switch connected in circuit with a trigger transformer and a capacitor charged from the high voltage power supply to trigger the flash lamps at the desired ten cycles per second rate. The existing flasher relay provides the alternate periods of multiple energization of each lamp at the rate of approximately 30 to 48 cycles per minute.

This invention relates to high intensity railroad crossing signals. More particularly, it relates to such crossing signals employing high intensity gas-filled arc discharge tubes.

The invention provides a pair of gas-discharge lamps mounted in a conventional railroad crossing signal installation. The lamps are alternately energized at substantially the same rate as the prior art incandescent lamps. However, the invention provides a plurality of flashes upon energization of each lamp. That is, each lamp is alternately energized at a rate of 30 to 48 times per minute and during energization each lamp is discharged or flashes approximately five times. We have found that this rate gives the greatest visibility and psychological impression of intensity and that the lamps appear to the observer to be on and off for approximately equal durations although, of course, each discharge in the lamps exist for only a few milliseconds; the longer duration psychological impression being provided by persistence of vision.

The invention provides a high intensity railroad crossing signal as above-described without fundamentally altering an existing crossing signal installation. That is, the discharge lamps are mounted within the pre-exist-ing lamp housings; the alternate flashing of the lamps is provided by the existing flasher relay; and electrical power supplied by the flasher relay is utilized by a novel control circuit, also mounted to the pole of the crossing signal, to energize the discharge lamps with a high voltage and to provide 3,390,304 Patented June 25, 1968 "ice trigger signals to flash them at the preferred rate of approximately five flashes per energization.

As automobiles have become increasingly powerful in the past twenty years, road traffic speed has greatly increased. This is true not only of limited access so-called superhighways but also of secondary roads that do have grade crossings and road intersections. Especially high speeds are prevalent in the great plain areas stretching bet-ween the Appalachians and Rocky Mountains of the United States. As average speeds have increased, highway engineers have recognized that traffic signals must be made more visible at greater distances in order to be effective. It has been found that the standard 69 Watt incandescent lamp for a red signal is no longer sufficient. Wattage has steadily increased to 150, then to 200 watts; 500 watt lamps are being proposed for some newer installations. Highway engineers have been able to utilize such'high power lamps because their trafiic signals are connected to ordinary alternating current power lines. However, the railroads have not been able to employ such high intensity lamps because of the requirement that signals at railroad grade crossings have standby battery power to be capable of operating during a power failure.

We realized that other forms of lamps existed which were more eflicient use-rs of power than incandescent lamps. One of these, which is particularly efficient and converts nearly all of the electrical energy used to visible light, is the gas-discharge lamp such as now commonly used to replace flashbulbs in photography. However, we found that such flash lamps could not be eflectively used in the same way that prior art incandescent lamps were utilized in a railroad crossing signal; that is, by merely alternately energizing the lamps from one arm to the other of the signal at the rate of 30 to 48 cycles per minute. Such a railroad signal we found was very effective at night. However, during the daytime the effectively perceived flash, being no longer than approximately onetwentieth of a second, (the persistence of vision of the average observer) would not be noticed in the bright sunlight.

Fortunately, we later discovered that a series of flashes from a gas-discharge lamp for the same duration of time that the incandescent lamp of a prior art railroad crossing signal is illuminated was perceived in daylight and was much more effective than the prior art incandescent lamps both day and night.

It is, therefore, an object of the present invention to provide a high intensity railroad crossing signal.

Another object of the invention is to provide such a railroad crossing signal at existing railroad crossing signal installations.

A further object of the invention is to provide such a high intensity railroad crossing signal utilizing substantially the same amount of power as existing railroad crossing signals.

A yet further object of the invention is to provide such a high intensity railroad crossing signal utilizing gas-discharge lamps.

Another object of the invention is to provide such a high intensity railroad crossing signal exhibiting psychological high intensity and visibility during daylight.

Still another object of the invention is to provide such a high intensity railroad crossing signal providing lamp life equal to or greater than that of the prior art incandescent lamps used in railroad crossing signals.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed disclosure taken in connection with the accompanying drawings in which:

FIGURE 1 is a side elevation of an existing railroad crossing signal installation in which the high intensity railroad crossing signal of the present invention is employed.

FIGURE 2 is a block diagram of the high intensity railroad crossing signal of FIGURE 1; and

FIGURE 3 is a schematic electrical circuit diagram of the high intensity railroad crossing signal of FIGURE 1.

The same reference characters refer to the same elements throughout the several views of the drawings.

Now referring to FIGURE 1, an existing railroad crossing signal installation is generally indicated at 20. It comprises the usual mast 22, crossed warning signs 24, cross arm 26, and lamp housings 28-28. Also mounted to the mast 22 is a control box 30 in which is mounted the flasher relay of the prior art.

According to the present invention, gas-discharge lamps are mounted within the housings 28-28 and the existing Fresnelled red lenses 32-32 are removed and replaced by plain glass red filters. A high voltage power supply and lamp pulsers are mounted in control box 34, also mounted to mast 22. Power is supplied from the flasher relay to control box 34 via cable 36 and high voltage and trigger pulses are supplied from control box 32 to the lamps in housings 28-28 via cables 38-38.

Within the control box 30 there is provided at the prior art installation a source of minus 12 volts DC power and this is supplied to the system at terminal 40 (FIGURE 2). The 12 volts is supplied to the existing flasher relay 42 and it alternately energizes conductors 44-44 at a rate of 30 to 48 cycles per minute; this being standard in the railroad industry. It is approximately the rate of lantern swinging of the average crossing attendant replaced by the automatic signal.

A high voltage power supply 46 is connected to the flasher 42 via cable 47. It supplies high voltage continuously across the gas-discharge lamps generally indicated at 48-48. Pulsers 50-50 are provided and when energized -via their respective conductors 44-44, they produce pulses at an approximate rate of ten per second. These pulses are supplied via cables 38-38 to trigger transformers 52-52, which may be supplied by the manufacturer of the discharge lamps 48-48 and are preferably mounted within the lamp housings 28-28. The trigger transformers 52-52 produce in response to each pulse supplied by the pulsers 50-50 a high voltage triggering pulse that causes the lamps 48-48 to discharge. Each pulser is preferably adjusted to provide approximately five pulses during the period that the pulser is energized by the flasher relay.

In order to make the most effective use of the available power, the circuit is adjusted so that the lamps 48-48 are discharged for approximately to milliseconds, this being the maximum average integrating time of the eye of a normal observer.

More specifically, and referring to FIGURE 3, the flasher relays of the prior art provide two pairs of terminals, left terminals 54 and right terminals 56 alternately energized at a rate of to 48 cycles per minute. The present invention provides some transient protection by connecting coils 58 and 60 and four-layer junction devices 62 and 64 as shown. These cause over-voltages across the terminals 54 and 56 to be harmlessly shorted and dissipated in the inductors 58 and 60 and in the other wiring in the control box 30 (FIGURE 1).

The negative terminals 54 and 56 are connected together by conductor 66. The positive terminals 54 and 56 are connected through inductors 58 and 60 and diodes 68 and 70 respectively to conductor 72. Conductor 72 is in turn connected to the emitters of high voltage power supply transistors 74-74. A capacitor 76 is connected between the cathodes of diodes 68 and 70 and the negative terminals 54 and 56. In a manner well known to those skilled in the art capacitor 76 is alternately charged and then discharged through a high voltage transformer 78 to produce a high voltage pulsating direct current through its secondary winding 80. Primary coils 82 and 84 are connected to the collectors of transistors 74-74 as shown; the midpoint between primary coils 82 and 84 being connected to the negative terminals 54 and 56. Positive conductor 72 is connected through a resistor 86 to coil 88. A resistor 90 is connected between the midpoint between coils 82 and 84 and the midpoint of coil 88. The output of high voltage transformer secondary 80 is filtered by resistor 92 and capacitor 94, which are connected in a voltage doubler arrangement with capacitor 96, diodes 98 and 100 and resistor 102. The resulting high voltage across terminals 104 and 106 is continuously applied across lamps 48-48.

In order to provide trigger pulses to the lamps 48-48, pulsers 50-50 are provided. The right pulsers 50R are connected through coil 60 and resistor 108 to right positive terminal 56. Capacitor 110R shorts transients to ground. A uni-junction transistor oscillator comprising uni-junction transistor 112R, capacitor 114R, resistors 116R and 118R, and variable resistor 120R is connected in circuit as shown. In accordance with principles well known in the art, when positive terminal 56 is supplied with power by the flasher relay 42 (FIGURE 2), capacitor 114R begins charging through resistors 108, 116R and 120R. No current flows through resistor 118R because the uni-junction 112 is an open circuit between its two base terminals. However, when the voltage across capacitor 114R reaches a value greater than the trigger voltage as determined by the intrinsic standoff ratio of the uni-junction 112R, the two bases become shorted and capacitor 114 is discharged through the trigger circuit 122R. After capacitor 114 discharges, the uni-junction 112R turns off and the action begins again. The rate at which this action takes place is determined by the charging time of capacitor 114R through variable resistor 120R. As previously stated, it is preferably adjusted to give approximately five flashes; that is, one each tenth of a second for the duration of illumination of the right hand lamp 48R.

The current of the discharging capacitor 114R passes through resistor 124R to fire the trigger of SCR 126R; the trigger being biased through resistor 128R. Shortcircuiting of the SCR discharges capacitor 130R through the primary 132R of trigger transformer 134R producing an extremely high voltage of approximately 10,000 volts across the secondary 136R. This is supplied to the trigger terminal 138R of the right lamp 48R. As is wellknown to those skilled in the art, trigger terminal 138R is connected to an encircling external electrode and the ions produced by energizing this electrode cause the flash lamp 48R to fire.

Capacitor 130R is charged through resistor 140R from the secondary 80 of the high voltage transformer 78. The left pulser 50L and left trigger circuit 122L operate in the same manner as described with reference to the right pulser 50R and right trigger circuit 122R. The components are given the same reference characters followed by L.

The values of the components illustrated in FIGURE 3 are as follows: Inductors 58 and 60 may be millihenrys; four-layer devices 62 and 64 may be GE type 6RS21SAIDI; diodes 68 and 70 may be Mallory type MR1031B; resistors 108 are 100 ohms; capacitor 76 is 500 microfarads, 25 volts; capacitors 110R and 110L are each 10 microfarads, 50 volts; transformer 78 may be a Triad type TY71S; transistors 74 may be type 2N458A, resistor 86 is 470 ohms, 1 watt; resistor 90 is 1.5 kilohms; resistor 92 is 750 ohms; 10 watts, capacitor 94 is 20 microfarads, 450 volts; capacitor 96 is a 10 microfarads, 600 volt, oil-filled capacitor; diodes 98 and 100 are Sarkes Tarzian Type F8, resistor 102 is a 750 ohm, watt resistor. The gas-discharge lamps are preferably a heavy gas type, such as an Amglo P/ N HD-3G that uses Xenon. When these lamps are used, Amglo type MT55 transformers 134R and 134L are used. In that case, SCRs 126 are Texas Instruments type 145A3; resistors 124 are 220 ohms; resistors 128 are 680 ohms; resistor 140 is 100 kilohms; and capacitor 130 is .22 microfarads, 400 volts.

In the pulser circuits 50, uni-junctions of type 2N2160 may be used. In this case capacitors 110 are 10 microfarads, 50 volts capacitors; resistors 116 and variable resistors 120 are 100 kilohmsresistors 116 being preterably of the deposited carbon type; resistors 118 are 180 ohms, and capacitors 114 are 2 microfarads, 100 volts.

In all cases above if the power capacity of the resistor is not given, it is one-half Watt.

It will be understood to those skilled in the art that many changes may be made in the above-described circuit of FIGURE 3 without departing from the scope of the invention. For example, various forms of oscillators may be employed for the pulsers 50R and 50L; various trigger circuits 122R and 122L may be employed. Furthermore, other high voltage power supplies may be utilized than that disclosed. However, it is a feature of the invention that the high voltage power supply that we do use is connected to the output of the existing flasher relay rather than 'being connected directly to the 12 volt supply at the signal installation.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A high intensity railroad crossing signal comprising:

(A) a spaced pair of very high intensity lamps;

(B) pulsing means for repeatedly automatically flashing a lamp at first repetition rate;

(C) and alternating means arranged to repeatedly automatically connect said pulsing means to said lamps alternately at a second repetition rate slower than said first repetition rate;

(D) the respective repetition rates of said means being such that the interval during which each lamp is continuously connected to said pulsing means is long enough to include a plurality of flashes by said pulsing means.

2. A high intensity railroad crossing signal as defined in claim 1 wherein said pulsing means energizes said lamps during each of said flashes for an interval of approximately 10 to 15 milliseconds.

3. A high intensity railroad crossing signal as defined in claim 1 wherein said pulsing means flashes each lamp approximately five consecutive times during each said continuous connection interval.

4. A high intensity railroad crossing signal as defined in claim 3 wherein said pulsing means flashes each lamp approximately every ten seconds whereby to produce the psychological impression that said lamp is on continuously half of the time.

5. A high intensity railroad crossing signal as defined in claim 2 wherein said pulsing means flashes each lamp approximately five consecutive times and then flashes the other lamp approximately five consecutive times.

6. A high intensity railroad crossing signal as defined in claim 5 wherein said alternating means connects said pulsing means to each lamp approximately 30 to 48 times per minute.

7. A high intensity railroad crossing signal system for installation in an existing railroad crossing signal comprising:

(I) a spaced pair of lamp housings;

(II) a direct current power supply; and,

(III) a flasher relay for alternately connecting said direct current power supply to a first and a second pair of flasher relay terminals;

said system comprising:

(A) a pair of high intensity gas discharge lamps mounted in said lamp housings respectively;

(B) a high voltage power supply connected to both pairs of said flasher relay terminals for applying a high voltage potential across said high intensity gas discharge lamps; and

(C) each of a pair of multiple impulse trigger circuits connected between a respective pair of said flasher relay terminals and a respective one of said gas discharge lamps to supply a multiplicity of trigger impulses to flash each of said lamps a plurality of times during the connection of the respective flasher relay terminals to said direct current power supply.

8. The system defined in claim 7 wherein each of said trigger circuits comprises a trigger transformer and a capacitor connected to said high voltage power supply and a solid state switch connected for discharging said capacitor through said trigger transformer.

9. The system defined in claim 8 wherein each of said trigger circuits comprises a unijunction transistor, resistor-capacitor, timing circuit connected to trigger one of said solid state switches.

References Cited UNITED STATES PATENTS 2,478,901 8/ 1949 Edgerton 315261 2,478,903 8/1949 Edgerton 31523O X 3,031,599 4/1962 Paschke 3l5201 3,113,293 12/1963 Bresse et al. 34083 X 3,267,328 8/1966 Girard 315l63 FOREIGN PATENTS 1,157,127 12/1957 France.

JAMES W. LAWRENCE, Primary Examiner.

C. R. CAMPBELL, J R. Assistant Examiner. 

